I have been using op-amp TL072C in charge integrator configuration.
R = 1k Ohms and C = 100 uF.
Vin is a DC signal of 1 V.
VCC = 10 V and VSS = -10 V.
I get the expected output which is VSS, when a DC signal given as input.
But the strange thing is that virtual ground voltage increases to about 0.65 V after output reaches VSS.
Attached the screen shot.
Why does the virtual ground voltage increases after output reaches to -VSS or saturation voltage ?
- Probe 3: Input
- Probe 1: Output
- probe 2: Virtual Ground
Best Answer
Is the question why it reaches 0.65 volts instead of 1 volt or is it about why it stops being a virtual ground?
An op-amp with negative feedback tries to maintain the inverting input at the same voltage as the non-inverting input by adjusting the output voltage so that the potentials are equalized. Once the op-amp output hits the end-stops, it no longer can continue to adjust the output in the correct direction to maintain a virtual earth.